Vanguard Vtwin 16hp with cam and rev kit

[BIKERMIKEYBLACK]

That idea putting the nut on the bottom of the rockers may work I’ll try that wen I readjust the valves 👍
I think the aluminum rockers are possibley stronger and maybe the stamped steel one are more cost effective

[slonomo]

Had some time today to work on the cart, since it warmed up to 38 degrees. It was bugging me that the valve lash adjusters were only on a couple threads worth so I decided to address that by moving the nut underneath as suggested.

Here's what they looked like before.

[slonomo]

The nut is 13mm, the Allen head is 5mm. Swapped them around without issue. Definitely more secure.

[slonomo]

Put the rockers back in, set the valve lash to .006", started it up, fired immediately.

The last time I drove it a month ago or so, I noticed the power felt down. Hmmmm. Well I thought maybe it was from the valve lash adjusters. Nope. Still idles funky. Reset the valves again, really carefully, and still same. Adjusted the pilot jet, still same.

So I did a leakdown test. Of course i had to loosen the rockers again. At 80 psi, leakage was only 2-3 psi. Repeated the test 3 times, same result. So 3.75% leakage is pretty good. I think the spec is 10%.

[slonomo]

Moved on to the compression test. Briggs doesn't have an official spec for compression. The manual says you just compare the two cylinders. More than 25% difference is too much.

Left cylinder was 40 psi
Right cylinder was 20 psi

Yes, I did the test several times with the throttle open.

[slonomo]

So with that information, I got my laser thermometer and checked the temp on the exhaust pipe nearest the head.

Left cylinder at 1000 rpm idle is 210 degrees, Right is 145 degrees.

At 3500 rpm, Left side is 605 degrees, Right side is 300 degrees.

So the Right cylinder is down 50% on compression compared to the left, and the Right cylinder is 50% colder.

This would explain the rough idle and black smoke on acceleration.

With this info, what do the engine mechanics think is going on?

[Field6565]

If I remember correctly. My Vanguard that was smoking bad had about 50 psi on each cylinder. After I put new rings in it I had a psi reading of 150 on one cylinder and 155 on the other. Might be time for a rebuild. Make sure you get the correct rings if you go this route. One set is thicker than the other.

[slonomo]

Thanks Gary.

This one doesn't smoke (oil smoke). It actually runs pretty good. Just has a little bit of a miss at idle, and when you rev it up it smokes from over fueling then clears up. Runs really nice at 3500 rpm, at least it sounds good.

The strange thing is the cylinder head/exhaust flange temp difference and the compression difference. Especially when the leakdown test showed almost no leakage.

[slonomo]

Well, after careful consideration, I have opted to remove and rebuild the 16hp engine.....but at a later date TBD.

The cart needs to be used around the house occasionally so at the moment I need a decently quick solution. After hearing another member's success, I have decided to replace it with a Predator 670. I obtained a coupon for $659, so with tax and $21 delivered to my door, the price for the 670 is $727.96. According to this other member and his thread, the engine should swap right in. I'll start another thread for the install.